Gonçalves RB*, Väisänen ML, van Steenbergen TJM, Sundqvist G and Mouton C.
Université Laval, Québec, Canada; FOP/UNICAMP, Brasil; National Public Health Institute, Helsinki, Finland; Academic Centre for Dentistry, Amsterdam, the Netherlands; University of Umea, Umea, Sweden.

Genomic fingerprints from 27 strains of Porphyromonas endodontalis of diverse clinical and geographical origins were generated as random amplified polymorphic DNA (RAPD) using the technique of PCR amplification with a single primer of arbitrary sequence (AP-PCR). From a total of 60 arbitrary primers 3 oligonucleotides 9- or 10-mer long were selected for their capacity to generate discriminatory fingerprints. Relatedness between the 27 strains was computed as distances based upon band sharing following analysis of the RAPD data obtained with each of the 3 primers. A matrix combining all the distances was then generated from which cluster analysis was performed by the unweighted pair-group method with mathematic averages and a dendrogram was constructed. We identified 25 distinct RAPD types which, at a dissimilarity level of 70%, clustered as 3 main groups thus identifying 3 genotypes. Genotypes I and II included exclusively P. endodontalis isolates of oral origin, while 7/9 human intestinal strains which linked at a similarity level of 52% constituted genotype III, the most homogeneous group of our study. Based on the RAPD genotypic diversity of 27 isolates we propose that three genotypes be recognized in the taxon P. endodontalis including two oral genotypes and one intestinal genotype.